The growth of environmental semiconductor β-FeSi_2 films for light emitting devices and photo-detection devices

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Orthorhombic the β-FeSi_2 is composed of nontoxic elements, which exist in great abundance on earth. The use of the β-FeSi_2 is expected in applications of thermoelectric devices, light emitting devices and photovoltaic cells. In this study, we attempted to grow the β-FeSi_2 thin film on Si substrate, using a pulsed laser deposition method (PLD), for investigating optical properties.(1)The β-FeSi_2 thin films were not grown at room temperature and substrate temperature over 400 degrees made the β-FeSi_2 monocrystalline structure.(2)The sample prepared on Si(111) substrate was a monocrystalline structure since only (202) or (220) signals of β-FeSi_2 were observed.(3)Composition of produced β-FeSi_2 was Fe:Si=30:70. So as-deposition β-FeSi_2 was Si-rich.(4)Iron was spread into Si substrate and the amount of diffusion was large at room temperature and 500 degrees.(5)β-FeSi_2/Si interface prepared by 400 degrees was an ideal one-side step junction.(6)When we used the annealing above 20 hours, the FWHM of β-FeSi_2 thin film was decreased about 50% and the crystalline recovery was observed. And β-FeSi_2 composition ratio was close to stoichiometry. And the band gap was increased.(7)Iron and a lattice defect were made impurity level and were considered to operate as a killer center of luminescence.(8)We found that the PL peaks from the β-FeSi_2 thin films on a Si substrate appear at 0.807eV for the samples annealed at 900℃ for 40h. The PL signal from the β-FeSi_2 thin film was observed using PLD for the first time to the best of our knowledge. And the PL peak of as-deposited sample is considered that Si defective peak ; and Si complex peak appeared.